1. Field of the Invention
This invention related to a method of purifying gases which are polluted by hydrocarbons and the like. The invention also relates to an apparatus which is usable for carrying out the method.
2. Description of the Prior Art
Authorities and the public have lately strongly increased the demands for a reduction of outlets of substances polluting the environment. Such substances can be hydrocarbons in solvents which are admixed to the ventilation air from an industrial plant.
There is today in the market an apparatus for purifying gases, for instance ventilation air having an admixture of hydrocarbons, the purification being made by catalytic combustion so that the hydrocarbons damaging for the environment are transformed to carbon dioxide and water. This apparatus comprises two reactors, each of which having a catalyst bed and a ceramic bed. The combustion reaction is exothermic, i.e. it emits heat. If the concentration of pollutions, i.e. in this case the content of hydrocarbons, is high enough, the combustion process becomes self-supporting, which means that no external energy needs to be supplied.
Heat emitted during the combustion reaction increases as the content of pollutions increases in the gas that shall be purified. This means that the temperature in the purification apparatus can be so high that the material is damaged. Owing to that the apparatus known in the market has limitations regarding the possibility to manage purification of gases having high contents of pollutions.
According to known technique there has been an attempt to solve this problem by making possible to take out gas to atmosphere at an area between the two reactors (see for instance EP-337 143). In order that this shall be acceptable from an environmental point of view, however, such a channel going out to the atmosphere has to be provided with a separate catalyst. This solution is of course both complicated and expensive.
This invention intends to offer a solution of the problem of purifying gases having high contents of pollutions, which solution is uncomplicated, relatively spoken, and attractive from an expenditural point of view. This has been made possible by a method of the kind mentioned by way of introduction, which is characterized by the moments mentioned in the claims.